Refactor VM and next instruction and argument reading

internal/vm/frame.go

@@ -14,18 +14,30 @@ type Frame struct {
 func NewFrame(cl *object.Closure, basePointer int) *Frame {
 	return &Frame{
 		cl:          cl,
-		ip:          -1,
 		basePointer: basePointer,
 	}
 }
 
-// NextOp ...
-func (f *Frame) NextOp() code.Opcode {
-	return code.Opcode(f.Instructions()[f.ip+1])
+func (f *Frame) ReadNextOp() code.Opcode {
+	op := code.Opcode(f.cl.Fn.Instructions[f.ip])
+	f.ip++
+	return op
 }
 
-func (f *Frame) Reset() {
-	f.ip = -1
+func (f *Frame) PeekNextOp() code.Opcode {
+	return code.Opcode(f.cl.Fn.Instructions[f.ip])
+}
+
+func (f *Frame) ReadUint8() uint8 {
+	n := code.ReadUint8(f.cl.Fn.Instructions[f.ip:])
+	f.ip++
+	return n
+}
+
+func (f *Frame) ReadUint16() uint16 {
+	n := code.ReadUint16(f.cl.Fn.Instructions[f.ip:])
+	f.ip += 2
+	return n
 }
 
 func (f *Frame) Instructions() code.Instructions {